There are three basic types of folded window coverings, pleated shade, cellular shades and Roman shades. The pleated type consists of a single layer of accordion folded or corrugated material. There is also a tabbed single layer of accordion folded or corrugated material which is disclosed in my U.S. Pat. No. 4,974,656. In a cellular shade pleated layers are joined together, or folded strips are stacked to form a series of collapsible cells. The cells may be symmetrical or D-shaped. Roman shades are a flat fabric shade that folds into neat horizontal pleats when raised. Roman shades may be a single sheet of material or may have a second sheet which acts as a liner. Cellular shades are known to have favorable thermal insulation properties because of the static air mass which is trapped between the layers of material when the cells are in the expanded position. The single-layer type, on the other hand, is favored for its appearance in some cases, and is less expensive to manufacture.
Conventionally cellular shades and pleated shades have been made from rolls of non-woven fabric material. In one method of manufacture, pleats or bonds are formed in the material transverse to the length of the roll and in the second method pleats or bonds are formed longitudinally along its length. The output of the transverse method cannot be wider than the roll width of the original material. The longitudinal method is limited in the types of patterns that can be printed on the material because alignment is random. The transverse methods have been limited to a single layer, a single tabbed layer or a triple layer where there are three continuous surfaces that create a panel of double cells.
In U.S. Pat. No. 4,685,986 Anderson discloses a method of making a cellular shade in which two single-panel pleated lengths of material are joined by adhesively bonding them together at opposing pleats. Other methods depart from this Anderson patent by joining together a series of longitudinally folded strips, rather than continuous sheets of pleated material. Such methods are shown in Colson U.S. Pat. No. 4,450,027, and in Anderson U.S. Pat. No. 4,676,855. In the Colson patent, strips of fabric are longitudinally folded into a U-shaped tube and adhered on top of one another, whereas in the Anderson patent these strips are Z-shaped and are adhered in an interlocking position.
Another method for making cellular shades is disclosed in U.S. Pat. Nos. 5,015,317; 5,106,444 and 5,193,601 to Corey et al. In that process fabric material is run through a production line that first screen prints the fabric and then applies thermoplastic glue lines at selected intervals. The fabric is then pleated, stacked, and placed in an oven to both set the pleats and bond the material at the glue lines.
The methods disclosed in these prior art patents require a substantial investment in capital equipment and are designed for large scale manufacture. Hence, these methods are not suitable for fabricators of custom shades who use woven and knitted fabrics.
There are many costs and problems associated with this method of making shades from rolls of fabric. First, the fabricator must store large rolls of material. Each roll must be hung on an axle which is stored in a rack to prevent damage to the material. If the roll is laid length wise on a flat surface over time the material will flatten over the contact area distorting the material. If the roll is stored on end and it tips the edge of the material can be damaged. There is also a practical limit to the width of material which can be purchased in rolls.
Another problem with this method of manufacture is that the fabricator must have a table wide enough and long enough to handle the largest shade which the fabricator will make. Consequently, fabrication space and inventory and handling are large and difficult.
For all these reasons there is a need for a method of manufacture of woven fabric cellular shades which should use less space and require less inventory, reduce fabrication and handling costs, and enable a greater variety of fabrics to be used including fabrics that can also be used for other products.
There is also a need for a pleated or cellular shade that is different in appearance from conventional shades on the market. Such a shade may have asymmetrical shaped cells or larger curved surfaces that appear to overcome the effects of gravity so that these shapes are maintained for the life of the product. The present invention meets those needs.